Staff reviewers for the Food and Drug Administration did not recommend the approval of Abbott Laboratories' implantable heart device MitraClip, citing a lack of "valid scientific evidence" of safety and effectiveness. FDA reviewers said in briefing documents, posted on the regulator's website on Monday, that approval of the device would not be appropriate at the time as major questions of safety, efficacy and overall benefit-risk profile remained unanswered. The device is being tested to treat mitral valve insufficiency - a disorder where a heart valve does not close properly when the heart pumps blood, causing blood to flow back into the heart - in patients considered high risk for open surgery. The device is inserted into the blood stream using a catheter. "The FDA staff is asking for more information. Abbott is conducting multiple trials on MitraClip, including the COAPT study, and the staff would want to look at that data," BMO Capital Markets analyst Joanne Wuensch said. The COAPT trial is testing the device in high-risk inoperable and high-risk mitral valve patients. Abbott has also recently developed a European trial for the patient population. Abbott had changed the proposed use for the device after the FDA expressed concerns that there was a lack of evidence to support its approval for a broader use in patients with significant mitral valve insufficiency, the reviewers said in the documents.